European Union foreign policy chief Catherine Ashton says Iran and world powers have held "substantive" and "useful" discussions at the second round of talks on a long-term settlement of the dispute over Iran's nuclear program.
Ashton said the sides would meet again in Vienna on April 7-9.
Ashton said the talks, which concluded on March 19 in the Austrian capital, dealt with Iran's uranium-enrichment activities, the future of Iran's heavy-water facility at Arak -- regarded as a possible source of plutonium -- and sanctions against the Islamic republic.
Iranian Foreign Minister Mohammed Javad Zarif appeared alongside Ashton and repeated her remarks in Persian.
In January, a six-month interim deal between Iran and the six powers -- Britain, China, France, Germany, Russia, and the United States -- went into force.